Preheat the oven to 400 degrees F. Lightly grease an 8-inch loaf pan or 8-inch square cake pan.
In a large bowl, combine the dry ingredients -- flour(s), baking powder, baking soda, and salt.
In a medium bowl, whisk the wet ingredients -- the maple syrup, egg, milk, and melted butter.
Pour the maple syrup mixture into the flour mixture and fold together until just combined. Gently fold in the blueberries.
Pour the batter into the prepared pan. Bake until golden brown and a toothpick inserted into the middle comes out clean - 50 to 60 minutes. (use convection at 375 degrees and it will cook a bit quicker)
Let the cake cool on a wire rack. If you are going to glaze the cake, set the wire rack over a sheet pan. Once the cake is cool, run the tip of a knife or spatula around the sides to loosen it. Place a plate over the cake and flip it over onto the plate, tapping the sides and bottom of the pan to make sure the cake is free. Remove the pan, turn the cake over and place it back on the wire rack over the sheet pan. (I just put in on a serving platter)
If using the glaze, add the maple syrup, butter, and salt to the small saucepan set over medium heat and stir until combined, then add the sugar and cook until it is dissovled. Pour the warm glaze over the cake, letting the excess glaze drip onto the baking sheet or serving platter. Slice and serve.